Percussion drilling method and apparatus



Feb. 22, 1966 N. T. BURDINE 3,236,313

PERCUSSIDN DRILLING METHOD AND APPARATUS Filed March 22, 1963 A 4 gm,

b. 61 F IG. 4. NATHAN THEODORE BURDINE INVENTOR.

ATTORNEY.

United States Patent (3 3,236,318 PERCUSSION DRILLING METHOD AND APPARATUS Nathan Theodore Burdine, Dallas, Tex., assignor to Socony Mobil Oil Company, Inc., a corporation of New York Filed Mar. 22, 1963, Ser. No. 267,196 3 Claims. (Cl. 175-106) This invention relates to a method and apparatus for drilling boreholes in earth formations. More particularly, this invention relates to the drilling of boreholes wherein a drill bit is operated under conditions of combined static and dynamic loading.

In conducting fatigue studies on rock, it has been discovered that the total amount of energy necessary to create rock failure rises exponentially as the amount of unit force imparted decreases. Stated otherwise, for a given degree of rock failure, a large number of low energy impacts consume appreciably more total energy than a much lower number of high energy impacts. Extrapolation of these findings into the field of conventional rotary drilling indicates that greater weights on a bit will cause formation rock failure with less total energy being consumed. While in conventional rotary drilling large amounts of weight may be placed on the drill bit, there are certain detrimental side effects which unnecessarily consume energy reducing the efficiency of the operation. The rock chips which are broken loose from the formation become trapped by the rolling cones of the bit, resulting in overdestruction of or crushing of the chips beyond the point necessary for effective drilling. Depending upon the character of the rock comprising the formation, the teeth of the rolling cones often must rise up on fresh rock which also unnecessarily expends energy because the entire drill string, including the static weight on the bit, must be lifted by the teeth in contacting the fresh rock. The energy necessary to rotate the bit to effect contact wtih fresh rock accomplishes little from the overall standpoint of efficient drilling of the formation. Thus, the net effect of conventional rotary drilling with the roller cone type bit is overdestruction of the rock since the bit is simply placed in contact with the formation under a static load and rotated,

Application of sudden dynamic loads to a drill bit has been carried out with the various forms of percussion drills. Generally, however, the known types of percussion drills do not lend themselves to the imposition of any appreciable static loading on the drill bit, and also they are not of a nature which permits concentration of the dynamic loading on any particular tooth or teeth of a drill bit.

It is an object of the present invention to provide a method and apparatus for drilling boreholes wherein simultaneous static and dynamic loading of a drill bit is possible. It is another object of the invention to provide a method and apparatus for drilling a borehole wherein there is no overdestruction of the rock chips broken loose from the formation during drilling. It is a further object of the invention to provide a method and apparatus for drilling boreholes which permit the imposition of high unit forces on the rock of the formation being drilled. These and still further objects of the invention will be evident from the following specification taken in conjunction with the accompanying drawings.

In accordance with one aspect of the invention, there is provided a method of drilling a borehole which includes the steps of imposing a static load on a drill bit and sequentially dynamically loading selective groups of the teeth of the drill bit. In accordance with another aspect of the invention, there is provided an apparatus Patented Feb. 22, 1966 for drilling a borehole which comprises incombination a drill bit having teeth which may be loaded statically and may be loaded dynamically in selected groups, means for' securing the drill bit to a drill string, and means for sequentially dynamically loading selected groups of the teeth of the drill bit.

In the drawings:

FIGURE 1 is a longitudinal view, partially in cross section and partially in elevation, illustrating one embodiment of the apparatus of the invention;

FIGURE 2 is a transverse view in cross section taken along the line 2-2 of FIGURE 1;

FIGURE 3 is a bottom view in elevation of the hammer employed in the apparatus of FIGURE 1; and

FIGURE 4 is a bottom view in elevation of the bit employed in the apparatus of FIGURE 1.

Referring to the drawings, housing 10 preferably comprises a tubular member which is secured at its upper end by any desired form of coupling, such as a threaded connection, to the lower end of a conventional type drill string, not shown. The drill string may include a number of sections of drill pipe and the requisite number of drill collars for imposing the desired static load on the drill bit. Secured to the lower end of housing 10 is a bit 11, the specific construction of which will be described hereinafter. Secured within housing 10 is an upper cylinder support 12 provided with a semicircular port 13 and a lower cylinder support 14 provided with a semicircular port 15. The upper surface of support 12 and the lower surface of support 14 slope toward their respective semicircular port to aid in reducing the turbulence of the drilling fluid flowing through the apparatus during operation. Secured between upper support 12 and lower support 14 is a cylinder As illustrated in FIGURE 2, partitions 21 and 22 extend from upper support 12 to lower support 14 between the outer wall of cylinder 20 and the inner wall of housing 10. Partitions 21 and 22 function to divide the annulus around cylinder 20 into semiannular passageways 23 and 24. Semiannular passageway 23 conducts fluid to the cylinder, while semiannular passageway 24 conducts fluid from the cylinder. Positioned within cylinder 20 is an internal liner or sleeve 25 which is of substantially the same length as cylinder 20 and thus is constrained from longitudinal movement within the cylinder. The tolerance between the outer wall of liner 25 and the inner Wall of cylinder 20 is such that the liner may be freely rotated within the cylinder for purposes of effecting the desired valve action, as will be explained. Both the cylinder and the liner are provided near their ends with a plurality of ports which, when brought into proper registry with each other by the rotation of the liner, permit fluid to enter into and be exhausted from the cylinder. For example, ports through the liner and cylinder, when in registry due to positioning the ports in the liner in line with the ports in the cylinder by rotation of the liner, allow fluid to flow from semiannular space 23 into the upper end of the cylinder. Ports 31' and 31 in the lower end of the liner and the cylinder, respectively, in the same manner permit the flow of fluid from semiannular passageway 23 into the lower end of the cylinder. Ports 32' and 32 at the upper end of the liner and cylinder, respectively, when in registry allow fluid to be exhausted from the upper end of the cylinder into semiannular passageway 24, while ports 33 in the lower end of the liner and cylinder in the same manner allow fluid to be exhausted from the lower end of the cylinder into semiannular passageway 24. The number of ports employed in the cylinder and liner and their exact positioning may be varied to achieve the desired valve action for any particular embodiment of the apparatus. In the particular embodiment illusrated, ports 31 and 32 would be open when it is desired that fluid enter the cylinder at its lower end from semiannular passageway 23 and leave the cylinder from its upper end through semiannular passageway 24. When fluid is to enter the upper end of the cylinder from passageway 23 and leave the lower end of the cylinder through passageway 24, ports 31 and 32 would be closed and ports 30 and 33 would be open. It will be readily recognized that the opening and closing of the desired ports is effected by rotation of inner liner 25 within cylinder 20.

Supported in cylinder within the inner liner is a piston 34 which is secured to a piston rod 35. Secured on the upper face of piston 34 are a plurality of pins 40, and secured on the lower face of the piston are a lurality of similar pins 41. Positioned around and secured to the inner wall of liner are a plurality of sloping vanes 42 and 43. The pins on the cylinder cooperate with the vanes on the inner wall of the liner to rotate the liner for properly positioning the ports in the liner. For example, as the piston moves toward the end of an upward stroke, pins 49 will contact vanes 42 causing movement of the vanes since the vanes are positioned at an angle with respect to the vertical. Movement of the vanes rotates the liner. In the same manner, downward movement of piston 34 will cause lower pins 41 to contact the lower vanes 43 which also will cause rotation of the liner 25 within the cylinder. The ports in the inner liner and cylinder, together with the pins on the piston and vanes within the liner, are all so located that when the piston has moved to the upper end of its stroke, ports and 33 will be open and ports 31 and 32 will be closed; and, when the piston has moved to the lower end of its stroke, the liner will have been rotated to the point where ports 30 and 33 will be closed and ports 31 and 32 will be open.

Piston rod extends through gland 44 secured in lower cylinder support member 14. Secured to the lower end of piston rod 35 is a hammer 45 which is provided with a plurality of passages 50 to permit the downward flow of the drilling fluid. Formed on the lower face of the hammer are a plurality of contact faces 51 which, in this embodiment of the invention, are three in number aligned as illustrated in FIGURE 3. Obviously, the number of contact faces may be varied as well as the positions of the contact faces. Also, the same pattern may be obtained by use of a continuous contact face rather than several separate ones to contact the number of teeth desired. Formed around the side wall of hammer 45 are a plurality of protruding guide pins 52. Formed in the inner wall of housing 10 is a continuous groove 53 which consists of vertical grooves 54 and sloping of angular grooves 55. Guide pins 52 engage groove 53, with the hammer being so oriented that during a downward stroke the guide pins will be in the vertical portions 54 and during an upward stroke the guide pins will engage the sloping portions 55 in order to effect rotation of the hammer. As the hammer moves to the upper end of each stroke, its guide pins will shift into the next adjacent vertical grooves to allow it to move downwardly without rotation. At the bottom of each stroke the guide pins will shift into the next adjacent sloping groove portions, causing the hammer to be rotated during the next upward stroke, etc. Obviously, groove 53, the guide pins on the hammer, together with pins and 41 on the piston, and vanes 42 and 43 within the liner, along with the ports in the cylinder and liner, must all be coordinated with respect to their positions in order to eifect smooth upward and downward movement and rotation of the piston, piston rod, and hammer. Also, groove 53 must be so located that the contact faces 51 on the hammer will strike the upper ends of the bitteeth on each downward stroke of the hammer.

Drill bit 11 comprises a collar or plate 60 and a plurality of teeth 61. Collar 66 is securely fixed to the lower end of housing 10 such that any weight imposed upon the housing by means of a drill string above the housing will in turn be exerted upon the teeth of the drill bit by means of the connecting collar 60. Each of teeth 61 is provided with a lower shoulder 61a and an enlarged upper portion 6112, providing an upper shoulder 61c. The tolerance between collar 60 and the teeth may be such as to provide a tight but sliding fit so that the teeth may move up and down or longitudinally within the collar. The upper ends of the teeth extend above the collar a sufficient distance to be contacted by faces 51. Lower shoulders 61a permit static loading of the teeth, while upper shoulders 61c prevent the teeth coming out of the collar when struck by faces 51. By providing a sliding fit between the teeth and collar, selected teeth may be dynamically loaded without appreciably affecting the other teeth. If very hard rock is to be drilled, however, the teeth may be fixed within the collar with the tooth movement resulting from dynamic loading being allowed by the elasticity of the material forming the collar. Extending through the collar are a plurality of ports 62 which should be adequate in size and number to provide a minimum amount of pressure drop in the drilling fluid passing through the plate. In determining the size and number of the ports 62, the structural rigidity of the complete bit must be taken into consideration. The exact design of the bit, including the geometry of the teeth, the number of teeth employed, and the positioning of the teeth in the bit, may be varied in accordance with the conditions under which the bit will be expected to drill. Among these conditions, of course, will be the characteristics of the rock comprising the formation through which the apparatus will be drilling a borehole.

In order to carry out one of the prime objectives of the invention, it is necessary that the designs of hammer element 45 and bit 11 be coordinated in order that selected groups of the teeth will be dynamically loaded sequentially by the percussive blows delivered by the reciprocating hammer. In the particular embodiment of the apparatus of the invention illustrated, the teeth of the drill bit 11 are struck in groups of three by the contact elements 51 on the hammer. The positioning of both the contact faces 51 and the upper ends of each of the groups of three teeth is such that when the hammer moves downwardly a solid impact 'blo-w will be delivered to each group of three teeth by the lower ends of the contact elements on the hammer. For purposes of illustration, reference is made to FIGURE 4 which shall be considered as showing three groupings of teeth designated by the dotted lines leading from the reference numerals 63, 64, and 65. For example, assuming on the first downward stroke of the hammer the three contact faces 51 strike the three teeth in group 63, then the hammer would be lifted and rotated 60 and again driven downwardly to strike group 64 of the teeth. The hammer would again be lifted and rotated such that on its next downward stroke it would strike the group 65 of the teeth. The hammer thus will beconstantly rotated and reciprocated, causing dynamic loads; or blows to be delivered to the teeth in groups of three to effect 'high concentrations of the available impact energy. The impact or dynamic loading i superimposed over the constant static loading placed upon the teeth: of the bit.

In operation, the apparatus of the invention is secured, on the lower end of a string of drill pipe and drill collar much in the same manner as conventional rotary drilling equipment. The drill collar is secured to the lower end of the drill pipe, and housing 10 of the apparatus of the invention is in turn secured to the lowermost section of the drill collar. The number of drill collars employed taken in conjunction with the weight of the drill pipe will be determined in accordance with the amount of static.

loading that is to be placed upon the bit. The number of drill collars may be increased or decreased as desired in order to obtain the desired amount of static loading or weight to be placed upon the drill bit. With the tool connected to the drill string, the drill string is lowered until the bit is in contact with the formation to be drilled and the entire weight of the drill string is allowed to constantly rest upon the bit with the weight being transferred to the teeth by contact of collar 69 on shoulders 61a. Flow of drilling fluid, which may be conventional drilling mud, air, gas, or water, depending upon the particular design of the tool of the invention, is then initiated through the drill string into the upper end of housing 10. The drilling fluid flows through port 13 in member 12 into semiannular passageway 23, from which it enters cylinder through the lower ports 31, The drilling fluid flowing into the cylinder under piston 40 causes the piston to be moved in an upward direction. At the upper end of its stroke, the pins 40 on piston 34 strike vanes 42, causing rotation of inner liner to effect closing of ports 31 and 32 and opening of ports and 33. The drilling fluid then enters the cylinder through ports 30 above piston 34, as shown in FIGURE 1, causing the piston to be driven in a downwardly direction, with the drilling fluid below the piston being exhausted into semiannular passageway 24 through lower ports 33. The driving of the piston downwardly causes downward movement of hammer 45. The guide pins 52 on the hammer will follow the straight portions 54 of the groove 53 in the inner wall of housing 10, effecting straight-line motion of the hammer toward bit 11. At the lower end of its downward stroke, contact faces 51 on the hammer strike the upper ends of a group of three of the teeth of bit 11, dynamically loading the teeth. For purposes of this discussion, it shall be assumed that the first impact of the hammer against the bit will cause the striking of group 63 of the teeth, as illustrated in FIGURE 4. At the lower end of the travel path of the piston and cylinder, pins 41 on the lower face of the piston will strike vanes 43 to rotate the inner liner and ports 31 and 32. Fluid then enters the cylinder through the ports 31 and exhausts from the cylinder through ports 32 to cause upward movement of the piston and hammer. As the piston and hammer move upwardly, the guide pins 52 on the hammer follow the angle portions 55 of groove 53 so that on the next downward stroke of the hammer the contact faces 51 will strtike group 64 of the teeth of the hit. As the hammer begins the upward stroke, pins 52 are initially biased into the inclined portions 55 of continuous groove 53 because of the camming action between pins 41 and vanes 43. That is, as the reaction between pins 41 and vanes 43 tends to rotate vanes 43 and therefore liner 25 in a clockwise direction, as viewed from the bottom of the housing 10, the inherent opposing reaction will tend to rotate piston 34 and hammer in the opposite, i.e., counterclockwise, direction. This counterclockwise rotational force applied to the hammer will of course tend to move pins 52 into the inclined slots as the hammer is moved upwardly relative to the housing 19. The upward and downward movement of the piston and hammer continues, with the next group of teeth being dynamically loaded being group 65. The sequential dynamic loading of the teeth of the bit will continue so long as the tool is operated, with the order of the groupings of teeth being that illustrated in FIGURE 4. Continually during the operation of the tool as described, the drilling fluid flows downwardly from semiannular passageway 24 through the passages 59 in the hammer and subsequently through the ports 62 in drill bit 11 into the actual area of drilling to wash the cuttings upwardly through the annular space around the tool within the borehole. The cuttings move to the surface with the drilling fluid, and the drilling fluid is treated to remove the cuttings and returned to the drill string in the manner employed in conventional rotary drilling. As the chipping of the rock of the formation continues through the mechanism of the combined static and sequential dynamic loading of selected groups of the teeth of the bit, the drill string is constantly lowered in order to maintain the bit teeth in contact with the rock under the desired static loading condition. It is to be emphasized that throughout the drilling process the drill string is moved only in a longitudinal direction, that is, it is restrained from rotation, thus avoiding the trapping and consequent overdest-ruction of rock chips which have been previously cut by adjacent bit teeth, as occurs in the use of a conventional roller cone type bit in rotary drilling.

It will be readily apparent to those skilled in the art that forms of mechanical structure other than the embodiment illustrated may be employed to carry out the method of the invention. For example, in lieu of the pistoncylinder-hammer combination illustrated, a fluid turbineactuated device may be utilized. Axially reciprocating pistonlike hammers may be provided to contact the upper ends of the teeth, with the pistons being reciprocated by a cam connected to the fluid turbine wheel. In such an arrangement, the cam surfaces would be so designed that selected groups of pistons would be simultaneously reciprocated to effect the sequential dynamic loading of the groups of bit teeth as described above.

What is claimed is:

1. In apparatus for drilling a borehole in an earth formation, the combination which comprises:

(a) a housing adapted to be secured to a drill string;

(b) a drill bit secured to the lower end of said housing, said drill bit including a plurality of teeth;

(c) means for securing said teeth in said drill bit in a. manner permitting the imposition thereon of both static and dynamic loads;

(d) a hammer in said housing having a portion on the lower face thereof to contact the upper ends of a selected group of said teeth, said hammer being reciprocable along the longitudinal axes of said drill bit and said hammer and rotatable about the longitudinal axes of said hammer and said bit in accordance with a preselected pattern whereby said hammer will strike a group of said teeth at the lower end of each of its downward strokes, the group of teeth struck on each downward stroke being diiferent from the group of teeth struck on the immediate past downward stroke;

(e) means associated with said housing and said hammer for eifectin'g rotation of said hammer in accordance with said preselected pattern; and

(f) fluid actuated means for causing said hammer to reciprocate.

2. In apparatus for drilling a borehole in an earth formation, the combination which comprises:

(a) a housing adapted to be secured to the lower end of a drill string;

(b) a drill bit secured to the lower end of said housing, said drill bit including a plurality of teeth;

(0) means securing said teeth in said drill bit in a manner permitting imposition on said teeth of both static and dynamic loads;

(d) a hammer positioned within said housing above said drill bit, the lower face of said hammer being formed to contact defined groups of the upper ends of said teeth;

(e) means associated with said hammer and said housing for guiding said hammer through a controlled pattern of straight-line longitudinal downward strokes and rotational upward strokes, said hammer on each downward stroke striking one of said defined groups of the upper ends of said teeth, the group of teeth contacted by said hammer on each downward stroke being difierent from the group contacted on the previous downward stroke due to the rotation effected in said hammer during each of said upward strokes;

(f) a connecting rod secured to said hammer;

(g) a piston connected to said connecting rod;

(h) a cylinder around said piston; and

(i) valve means associated with said cylinder for controlled admission of fluid to cause reciprocation of said piston.

3. In apparatus for drilling a borehole in an earth formation, the combination which comprises:

(a) a housing adapted to be secured to the lower end of a drill string;

(b) a plate secured across the lower end of said housing, said plate having ports to all-ow fluid to flow therethrough;

(c) a plurality of teeth secured through said plate in a substantially uniform pattern, the upper ends of said teeth extending above said plate;

((1) means for securing said teeth through said plate in a manner permitting the imposition thereon of both static and dynamic loads;

(e) a hammer in said housing above said teeth, said hammer having at least one contact face on the lower surface thereof for striking the upper ends of selected groups of said teeth;

(f) said housing being-provided in the region of said hammer with a continuous internal groove having interconnecting alternate longitudinal and sloping portions;

(g) guide pins on the side wall of said hammer to cooperate with said groove in said housing to direct said hammer through a series of alternating longitudinal downward strokes and upward rotating strokes whereby said contact face on said hammer will progressively deliver impact blows to the upper ends of said teeth in selected groups;

(h) a connecting rod secured to the upper side of said hammer;

(i) -a piston secured to said connecting rod;

(1) .a cylinder within said housing around said piston,

said cylinder having ports at opposite ends to permit fluid to enter and be exhausted from said cylinder for causing said piston to reciprocate;

(k) a rotatable liner within said cylinder around said piston, said liner having ports to cooperate with said ports in said cylinder to control fluid flow into and out of said cylinder;

(1) means on said piston and said liner adapted to cooperate whereby reciprocation of said piston effects rotation of said liner to position said ports in said cylinder and said liner for control of fluid into and out of said cylinder; and

(m) means for supporting said cylinder within said housing including upper and lower support members and partition members extending between said cylinder and the inside wall of said housing dividing the annulus between said cylinder and said housing into a passageway for directing fluids entering said cylinder and a passageway for directing fluids being exhausted from said cylinder.

References Cited by the Examiner UNITED STATES PATENTS 148,393 3/1874 White 91-276 1,087,632 2/1914 Benjamin -381 X 1,612,338 12/ 1926 Wilson et al 175-381 X 1,710,925 4/1929 H ardsocg 175-296 X 1,891,416 12/1932 Harris 175-381 X 2,072,470 3/ 1937 Thompson 175-319 2,350,364 6/1944 Menhall 175-101 2,400,853 5/1946 Stilley 175-106 2,942,850 6/1960 Heath 175-296 X CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN HERSH, Examiner. 

1. IN APPARATUS FOR DRILLING A BOREHOLD IN AN EARTH FORMATION, THE COMBINATION WHICH COMPRISES; (A) A HOUSING ADAPTED TO BE SECURED TO A DRILL STRING; (B) A DRILL BIT SECURED TO THE LOWER END OF SAID HOUSING, SAID DRILL BIT INCLUDING A PLURALITY OF TEETH; (C) MEANS FOR SECURING SAID TEETH IN SAID DRILL BIT IN A MANNER PERMITTING THE IMPOSITION THEREON OF BOTH STATIC AND DYNAMIC LOADS; (D) A HAMMER IN SAID HOUSING HAVING A PORTION ON THE LOWER FACE THEREOF TO CONTACT THE UPPER ENDS OF A SELECTED GROUP OF SAID TEETH, SAID HAMMER BEING RECIPROCABLE ALONG THE LONGITUDINAL AXES OF SAID DRILL BIT AND SAID HAMMER AND ROTATABLE ABOUT THE LONGITUDINAL AXES OF SAID HAMMER AND SAID BIT IN ACCORDANCE WITH A PRESELECTED PATTERN WHEREBY SAID HAMMER WILL STRIKE A GROUP OF SAID TEETH AT THE LOWER END OF EACH OF ITS DOWNWARD STROKES, THE GROUP OF TEETH 